Mark Dominus
blog.plover.com · Personal blog · on HN since 2007
Mark Dominus writes The Universe of Discourse, covering math, programming, languages, and miscellaneous curiosities since 2006.
What HN saysHN commenters recommend it as a blog consistently worth reading, describing it as about one-third math and the rest everything else, often reaching the front page.
326HN people shared it
157linked it in comments
451stories submitted
18Kstory points
2 months agolast shared
2007people per year2026
Most-shared posts
- 1Monads are like burritos (2009)22 people · 131 points · first shared 2009 · 136 comments on HN
- 2Homepage12 people · first shared 2007
- 3Design Patterns of 1972 (2006)10 people · 55 points · first shared 2008 · 10 comments on HN
- 4Why I like Java9 people · 443 points · first shared 2014 · 425 comments on HN
- 5Why Lisp Will Never Win (2003)9 people · 195 points · first shared 2010 · 100 comments on HN
- 6“Design Patterns” Aren't (2002)8 people · 563 points · first shared 2008 · 122 comments on HN
- 7One Plus One Equals Two (2006)8 people · 118 points · first shared 2018 · 61 comments on HN
- 8Conference Presentation Judo7 people · 50 points · first shared 2008 · 13 comments on HN
- 9Arithmetic with Continued Fractions7 people · 6 points · first shared 2009 · discussion on HN
- 10Moonpig: a billing system that doesn't suck6 people · 78 points · first shared 2013 · 58 comments on HN
- 11Perl Regular Expression Matching Is NP-Hard6 people · 44 points · first shared 2015 · 18 comments on HN
- 12A message to the aliens (introduction)6 people · 4 points · first shared 2015 · 6 comments on HN
- 13How Regexes Work5 people · 87 points · first shared 2007 · 10 comments on HN
- 14Continued Fraction Arithmetic (1972)5 people · 19 points · first shared 2016 · 7 comments on HN
- 15NPC 3SAT5 people · first shared 2009
What HN people wrote when they linked it
mjd · 2023-07-07
https://blog.plover.com/ The Universe of Discourse, since 2006.
About ⅓ math and ⅔ everything under the sun.
Hits the front page here several times a year.
A few of my favorites:
* https://blog.plover.com/lang/middle-english.html You can learn to read Middle English
* https://blog.plover.com/math/60-degree-angles.html 60-degree angles on a lattice
* https://blog.plover.com/math/24-puzzle-2.html Recognizing when two arithmetic expressions are essentially the same
rincewind · 2012-09-01
Are you thinking about Mark Jason Dominius? His Web site is http://perl.plover.com/. He made a presentation about making presentations at OSCON: https://www.youtube.com/watch?v=I_Tsom5hI98
Stephen Bond, who wrote the linked page, is at http://plover.net/~bonds/. I could not find any OSCON talks by him. Can you please provide a link? I think you are confusing them based on the similar domain names.
btilly · 2012-07-15
How did this wind up here?
For the original, go to http://plover.com:8080/~alias/list.cgi?2:mss:234:200507:hoknbblkgieoac… and see the discussion we had about it then.
It is also worth noting that MJD has the distinction of being the highest rated speaker at Oscon ever. If there is any possibility of interest, he is worth watching because he is incredibly informative.
See http://perl.plover.com/ for some of his older Perl writings.
4ad · 2011-12-12
Doug McIlroy[1] invented pipes, by the way. He's also the author of spell, diff, sort, join, graph, speak and tr. He has written some fascinating papers, like Squinting at Power Series[2].
Thanks Christian Neukirchen for posting this on his blog[3], Mark Dominus[4] for asking for a copy and Doug McIlroy for sharing in the first place.
[1] http://www.cs.dartmouth.edu/~doug/
[2] http://swtch.com/~rsc/thread/squint.pdf
[3] http://chneukirchen.org/trivium
[4] http://blog.plover.com
10ren · 2009-04-04
Perl, like other scripting and late-binding languages, is very flexible ("duct tape of the internet"). Amazon is reputedly a Perl shop and it gives them agility to quickly experiment with new retailing ideas. But the knowledge they gained, and the site they built, wasn't due to Perl - it was due to them working on problems they found.
Here's someone else who solves problems: http://blog.plover.com (and who wrote Higher Order Perl).
All learning is commendable, including learning from a language. But to think that knowledge comes only from existing languages is to constrain one's knowledge, and for oneself to be defined by one's tools. Languages aren't the source of intellectual nutrition; they are a conduit to it (or how could they be created in the first place?). The source is creating solutions to problems.
jrockway · 2009-01-30
I enjoy random blogs (yay for link agregation sites), but MJD and Steve Yegge continually write content worth reading:
MJD: http://blog.plover.com/
Yegge: http://steve-yegge.blogspot.com/
anthonyrubin · 2008-11-29
A few I haven't seen mentioned:
http://blog.plover.com/
http://www.aaronsw.com/weblog/
http://neopythonic.blogspot.com/
LukeShu · 2019-01-16
I agree with sjburt when he says "I think once you understand the graph, then looking at what the graph looks like and what you want it to look like usually leads you to being able to figure out what operation you want." When I was first getting in to Git ~10 years ago, I remember that I found the PeepCode "Git Internals" book[1] very helpful for getting that understanding of the graph.
Once you have the better understanding of the graph, it's hard to find resources on how to improve from there; most resources focus on beginner stuff, or function more as a technical reference without really talking about use-cases. I've found following Mark Dominus' blog[2] for his posts about Git to be the single best thing to "level up" my Git usage once already being at a high-level.
[1]: At the time, I had to pay money for the eBook, now they have the whole thing on GitHub: https://github.com/pluralsight/git-internals-pdf
[2]: https://blog.plover.com/
absconditus · 2011-10-17
tristramb · 2026-08-13
"Principia Mathematica is an odd book, worth looking into from a historical point of view as well as a mathematical one. It was written around 1910, and mathematical logic was still then in its infancy, fresh from the transformation worked on it by Peano and Frege. The notation is somewhat obscure, because mathematical notation has evolved substantially since then. And many of the simple techniques that we now take for granted are absent. Like a poorly-written computer program, a lot of Principia Mathematica's bulk is repeated code, separate sections that say essentially the same things, because the authors haven't yet learned the techniques that would allow the sections to be combined into one."
- Mark Dominus (https://blog.plover.com/math/PM.html)
whilenot-dev · 2026-07-02
Thank you, I thought I was getting crazy! The self-proclaimed amateur mathematician[0] who quotes his own writing in 3rd person has some stuff to work on I guess.
[0]: https://blog.plover.com/meta/about-me.html
Dig1t · 2026-04-30
So weird, on the front page at the same time as this: "Biology is a burrito"
When I saw that link it immediately reminded me of this: https://blog.plover.com/prog/burritos.html
>Monads are like burritos
And then a few links down is this link to monad tutorials.
Weird coincidence.
ducklord · 2026-04-30
> Monads are like burritos https://blog.plover.com/prog/burritos.html
I'm surprised that this tutorial isn't on the wiki.
gbacon · 2026-02-27
Ah, but then there are the unusual cases. See “The shell and its crappy handling of whitespace.”
https://blog.plover.com/Unix/whitespace.html
svat · 2025-11-28
(2016)
Also, “direct” link: https://blog.plover.com/tech/tmpdir.html (This doesn't really matter, as the posted link is to https://blog.plover.com/2016/07/01/#tmpdir i.e. the blog post named “tmpdir” posted on 2016-07-01 and there is only post posted on that date, so the content of the page is basically the same.)
creata · 2025-08-27
Here's another one by Gosper, with the famous quote:
> Abstract: Contrary to everybody, this self contained paper will show that continued fractions are not only perfectly amenable to arithmetic, they are amenable to perfect arithmetic.
https://perl.plover.com/yak/cftalk/INFO/gosper.txt
johnea · 2025-02-11
Why is anything? I see no point in the feature.
One is always free to not read any comments that one does not wish to see...
Some people just enjoy the disruption of convesation.
Apropos:
Just give the man the fish (i.e. just answer the question) [4 camtarn]
https://blog.plover.com/misc/just-answer-the-question-2.html
https://news.ycombinator.com/item?id=43002679
jdnier · 2025-02-10
Interesting article relating Adam Unikowsky asking for Claude to decide a Supreme Court case: https://blog.plover.com/tech/gpt/presidential-emoji.html
"Claude is fully capable of acting as a Supreme Court Justice right now."
tomrod · 2024-12-28
If this is new, then you're one of today's luck 10,000![2] Serious logical foundations take a lot of time and exposition to start from fundamentals. Dismissing them as non-serious because GP's argument failed to consider them is misguided, IMHO.
[0] The classic reference: https://en.wikipedia.org/wiki/Principia_Mathematica -- over 1,000 pages, Betrand Russell
[1] https://cmartinez.web.wesleyan.edu/documents/FP.pdf -- a bit more modern, relying on other mathematics under the hood (like DRY reduces the base count), 11 pages
[2] https://xkcd.com/1053/
[3] Some reasonable review https://blog.plover.com/math/PM.html
petesergeant · 2024-11-23
> it is always interesting what is an acceptable trick and what is not
I have not found the type of person who asks trick questions to be the type of person who finds it interesting to have the trick questions they've posed to be prodded.
Completely tangential, but something I enjoyed reading that feels in the same realm: https://blog.plover.com/math/logic/annoying-boxes-solution.html
ngcc_hk · 2024-10-23
Tw there is a follow-up. Not much. But still an update : https://blog.plover.com/math/PM-translation.html
a1369209993 · 2024-09-26
n4r9 · 2024-07-04
It's a weird example, but what about
a 1 b 101 ?
It is neither prefix-free nor suffix-free. Yet every occurrence of 0 corresponds to an occurrence of b.
However, this is obviously inefficient. So I guess the question is whether there's an optimal code which is neither prefix-free nor suffix-free.
--------------
EDIT
I did some googling and found this webpage https://blog.plover.com/CS/udcodes.html where the author gives the following example of a uniquely decodable code:
a 0011 b 011 c 11 d 1110 I guess this is "almost" prefix-free since the only prefix is c of d. If a message starts wiht 1, you could find the first 0 and then look at whether there's an odd or even number of 1's. So I think I can see how it's uniquely decodable. However, my crypto knowledge is too rusty to remember how to show whether this is an optimal code for some probability distribution.
burntsushi · 2024-05-21
As the OP specifically and explicitly says, back-references are definitively NP-complete. The OP even links to a proof[1]. If you found a way to implement them in worst case linear time, then I believe you would have discovered a constructive proof for p=np.
Look-around is a different story, but I don't believe you can still guarantee linear time.
[1]: https://perl.plover.com/NPC/NPC-3SAT.html
fargle · 2024-05-15
link went bad, this works: https://blog.plover.com/tech/its-an-age-of-marvels.html
WorldMaker · 2024-04-22
The Dymaxion projection came up in my own recent reading because one was sent in the "Cosmic Call": https://en.wikipedia.org/wiki/Cosmic_Call
The blog series I was reading: https://blog.plover.com/aliens/dd/intro.html
The Cosmic Call map was specifically pages 19-20: https://blog.plover.com/aliens/dd/p19.html
gmfawcett · 2024-02-27
Whenever someone mentions building a billing system, I feel compelled to share Mark Dominus' delightful article, "Moonpig: a billing system that doesn't suck":
> Sometimes I see other people fuck up a project over and over, and I say “I could do that better”, and then I get a chance to try, and I discover it was a lot harder than I thought, I realize that those people who tried before are not as stupid as as I believed. That did not happen this time. Moonpig is a really good billing system. It is not that hard to get right. Those other guys really were as stupid as I thought they were.
https://blog.plover.com/prog/Moonpig.html
082349872349872 · 2023-11-15
if not part of public education, one would hope that it might at least be provided at home, eg https://blog.plover.com/lang/embedded.html
master-lincoln · 2023-10-04
apparently the words strong and weak typing have no agreed upon definition so they can not be meaningfully discussed without stating your definition.
e.g. https://perl.plover.com/yak/12views/samples/slide045.html
Nzen · 2023-09-19
I enjoyed Mark Dominus's blog post [0] about the billing system he cowrote, moonpig. It restates much of the other responses, namely that ignoring infinitesimal errors/rounding would have instilled a culture of - at minimum - doubt. Perhaps another way to see this is to look at a visualization [1] of the discontinuous coverage that floating point gives to the numbers we want to represent.
[0] https://blog.plover.com//prog/Moonpig.html#fp-sucks
[1] https://observablehq.com/@rreusser/half-precision-floating-point-visua…